Re: [Flexradio] Audiocards, USB, etc.
Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise in the present computer environment and with signals approaching the thermal noise levels are challenging. Instead of measuring the audio card only I decided to continue with the whole SDR-1000 system. I recorded 1) the noise floor (dBm/500 Hz) with audio card input cable input connected to the radio and the antenna connector terminated to 50 ohm and then 2) with a signal to radio until clipping or compression was indicated at the line-in connector of the radio or at the SDR-1000 own measurement systems. The results were: Preamp Setting HIGH, -140 dBm/500 Hz, -26 dBm, INA163 out 25 Vpp Preamp Setting MED, -130 dBm/500 Hz, -16 dBm, INA163 out 25 Vpp Preamp Setting LOW, -130 dBm/500 Hz, -13 dBm, INA168 out 4.8 Vpp (1.4 dB compressed) My conclusion is that the QSD can take about 4 Vpp until it starts to saturate and my sound card can take 29 Vpp, so the amplifier after the QSD could have 17 dB voltage gain for optimal results. The front end gain need to be adjusted accordingly. Dan mentioned:... ideally 130 to 145 db to match the blocking performance of other rigs This should be our target and to achieve that we need audio cards handle signal from tens of nanovolts to tens of volts. I estimate, the accuracy of the above measurements is about 1 dB. The measurements were made with PowerSDR 1.4.5 console with unmodified RFE. These figures serve as the reference when comparing the results of the ECO-25 modifications. 73, Ahti OH2RZ - Original Message - From: Jim Lux [EMAIL PROTECTED] To: Tayloe Dan-P26412 [EMAIL PROTECTED]; Tayloe Dan-P26412 [EMAIL PROTECTED]; Ahti Aintila [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Sent: Saturday, September 24, 2005 6:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc. At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE Such tests would be useful, but are quite challenging to make for high performance systems. You can take two general approaches: 1) Obssessively account for all the error sources, use very clean sources, etc. so you can truly know that what you've measured is just the unit under test, and not quirks of the experimental setup. 2) Measure it in a typical setup, in which case the performance will certainly measure out worse, but at least it's representative of what you'll really get. Consider that if you're looking for 140 dB relative levels, you're looking for signals of a 0.1 microvolt on a 1 volt signal. I've done DC measurements to 6 digits, and it's, frankly, an ordeal. You'd also need sources that are that good, which is no easy matter, especially if you want to cover the full frequency span of the device (several decades). For instance, the SRS DS360 claims -100dBc distortion from 10mHz to 20 kHz. It's not too pricey at about $3000.
Re: [Flexradio] Audiocards, USB, etc.
I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Saturday, September 24, 2005 7:47 AM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise in the present computer environment and with signals approaching the thermal noise levels are challenging. Instead of measuring the audio card only I decided to continue with the whole SDR-1000 system. I recorded 1) the noise floor (dBm/500 Hz) with audio card input cable input connected to the radio and the antenna connector terminated to 50 ohm and then 2) with a signal to radio until clipping or compression was indicated at the line-in connector of the radio or at the SDR-1000 own measurement systems. The results were: Preamp Setting HIGH, -140 dBm/500 Hz, -26 dBm, INA163 out 25 Vpp Preamp Setting MED, -130 dBm/500 Hz, -16 dBm, INA163 out 25 Vpp Preamp Setting LOW, -130 dBm/500 Hz, -13 dBm, INA168 out 4.8 Vpp (1.4 dB compressed) My conclusion is that the QSD can take about 4 Vpp until it starts to saturate and my sound card can take 29 Vpp, so the amplifier after the QSD could have 17 dB voltage gain for optimal results. The front end gain need to be adjusted accordingly. Dan mentioned:... ideally 130 to 145 db to match the blocking performance of other rigs This should be our target and to achieve that we need audio cards handle signal from tens of nanovolts to tens of volts. I estimate, the accuracy of the above measurements is about 1 dB. The measurements were made with PowerSDR 1.4.5 console with unmodified RFE. These figures serve as the reference when comparing the results of the ECO-25 modifications. 73, Ahti OH2RZ - Original Message - From: Jim Lux [EMAIL PROTECTED] To: Tayloe Dan-P26412 [EMAIL PROTECTED]; Tayloe Dan-P26412 [EMAIL PROTECTED]; Ahti Aintila [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Sent: Saturday, September 24, 2005 6:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc. At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE Such tests would be useful, but are quite challenging to make for high performance systems. You can take two general approaches: 1) Obssessively account for all the error sources, use very clean sources, etc. so you can truly know that what you've measured is just the unit under test, and not quirks of the experimental setup. 2) Measure it in a typical setup, in which case the performance will certainly measure out worse, but at least it's representative of what you'll really get. Consider that if you're looking for 140 dB relative levels, you're looking for signals of a 0.1 microvolt on a 1 volt signal. I've done DC measurements to 6 digits, and it's, frankly, an ordeal. You'd also need sources that are that good, which is no easy matter, especially if you want to cover the full frequency span of the device (several decades). For instance, the SRS DS360 claims -100dBc distortion from 10mHz to 20 kHz. It's not too pricey at about $3000. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
At 02:45 PM 9/24/2005, Tayloe Dan-P26412 wrote: I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! - Dan, N7VE I'm sure if you tell them you've got guaranteed sales of 100 million units a year, they'll get right on it. grin I think we're in that niche market category. There have been some interesting analyses of speed vs bits performance for A/Ds over the years, and it seems that there are a few sweet spots that accomodate pretty much all architectures. In order to make an alternate architecture attractive, you'd have to go many orders of magnitude better. Here's an example. You've been able to get fast A/Ds (20 MSPS) in 12 bit accuracy for decades. (the AD9042 is a venerable example) This is low enough dynamic range that you need some selectivity in front of it. That is, you can use it at the IF, but you're not going to be able to hook an antenna up to the A/D input and build an all digital receiver. In order to do the latter, you need to have a lot more bits (like 20-24+), while keeping the same high sample rates. Going to 13 bits or 14 bits or 16 bits just isn't worth it, because you STILL won't have enough dynamic range to get rid of the first conversion or preselector, but you've got a MUCH more expensive A/D now. However, that same 12 bit accuracy has been getting faster (although not by a factor of 10...the 9042 is 41 MSPS, and I don't know that there are any 400 MSPS 12 bit A/Ds out there) The big change has been in improving the performance of those 12 bits:the 9042 is 10.5 ENOB, newer parts are better than 11, and the 9042 only achieves good performance at a limited range of sample rates, newer parts work at any sample rate. Most important to system designers is the reduction in the power consumption; that bipolar 9042 draws half a watt(!), and new CMOS versions draw a lot less. There's also a wider variety of packages and IC processes to choose from. Maybe you need some amount of radiation tolerance.. the bipolar 9042 is a rock, the CMOS parts are kind of soft. New SiGe or SoI parts might get you low power AND rad tolerance. In any case, we're sort of going to have to live with what ever the consumer market finds useful. Jim, W6RMK
[Flexradio] SDR1000 IQ Signal Recordings
I have a couple of simple questions to the group. I'm awaiting a SR-40 radio to come in, in the meantime I have setup several PC's to hook up the the radio, and I have installed the software. I noticed something funny last night, my other four PC's do the same thing. While listening to a IQ recording there is practically no noise at all, this a particular recording is of a 40 meter CW contest. Even when I tune in-between signals there is no noise. I played with the squelch settings, no change, the filters are off. My question is, when someone with a SDR1000 radio makes a recording does it record the raw band data, or does it record it after whatever filters the user has applied? I have several recordings and they are all the same, no noise. The funny thing is on the scope you can see noise and sometimes weak signals that rise about 4 to 7 db above the noise level and when you tune them you get nothing, no audio out, even when you can see a weak signal there. I'm using the version 1.4.4 with the Soft-Rock modifications, is there a bug where the squelch is on all the time? Setup; Dell Precision 220 2X Pentium III 512 Meg Ram Win2K SP4 .Net V1.1 SP1 DirectX 9 MDAC 2.8 SP1 Flex software with Soft-Rock patch V1.4.4 ASIO4All V1.8 (Latest), I tried ASIO and MME drivers, do difference. SB Live 24 (Pci), SB Live, SB Audigy 2 Zs, Built in SoundMax Digital Audio, I tried all these cards. The System is patched up with all the latest security patches from Microsoft. -- Cecil Bayona KD5NWA www.qrpradio.com I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...
[Flexradio] Fun with the SDR-1000
The other afternoon I was talking to a group of my friends on 40 meters when I remarked that one guy was wider than the rest. In order to illustrate this, I hit the standby tab and froze the panadapter display. I then did a screen capture and pasted it into PhotoEditor, cropped it, and made jpeg files of several of the signals for comparison. I emailed the guys these jpeg files. Well, this generated a lot of discussion that culminated with me sending my RealVNC authentication information to a couple of the guys. They were able to get on their computers and see their signals in real time. When lunch time came, I left the connection intact and let the guys play awhile. After lunch I gave one of them a tour of the radio while he watched on his computer screen as I described what I was doing on the radio. What a blast! Needless to say he was impressed! 73, Tom W0IVJ
